Going by the strings in the New_3DS Internet Browser main code binary, it appears these MVD services(or at least mvd:STD) are used for hardware video/media decoding.
MVD Service "mvd:STD"
This one uses the I/O mapped @ 0x10207000.
This service is used by the New_3DS Internet Browser.
MVD Service "l2b:u"
This one uses the I/O mapped @ 0x10130000.
MVD Service "l2b2:u"
This one uses the I/O mapped @ 0x10130000.
MVD Service "y2r2:u"
This one uses the I/O mapped @ 0x10102000.